Remove GITLAB_LEGACY_BACKGROUND_UPLOADS
When we removed background upload for object storage in GitLab 15.0 we left behind an escape hatch in case anyone got in trouble because of this change after upgrading. It has been 4 months and we think it is time to remove the escape hatch.
This commit removes support for the GITLAB_LEGACY_BACKGROUND_UPLOADS environment variable.
Also see epic gitlab-com/gl-infra&734 (closed).
Edited by Jacob Vosmaer